A leaf-mimicking katydid, Cratioma oculatum, of Southeast Asia
Leaf mimicry is the evolved resemblance of an organism to a leaf, a form of mimicry. This may serve directly as camouflage, or it may function as Batesian mimicry if the leaf model is distasteful, for example if it has chemical defences. The mimicking organism can be a plant, such as the vine Boquila trifoliata, or an animal. It is not known how the vine can sense different leaf shapes. Among animals, many leaf mimics are insects, especially butterflies, katydids, and phasmids. Others are vertebrates, including leaffishes and toads. The mimicry, both in insects and among vertebrates, can involve behaviour as well as coloration and body shape.
Fossil leaf-mimicking insects are known from the Jurassic of northeastern China, including both grigs and lacewings, and from a phasmid of the Eocene of Germany.
Boquila trifoliata, a South American member of the family Lardizabalaceae, is a climbing vine with a highly variable appearance (phenotype). It is capable of mimicking the leaf features of plant species that it clings to, such as their coloration, size, and shape. By camouflaging its leaves, Boquila reduces damage from herbivorous animals.[1] This is a form of Batesian mimicry, where B. trifoliolata is harmless but resembles a less palatable or harmful plant to ward off herbivory species and pests.[1][2][3]
It has been speculated that such plants may make use of "some kind of vision" using ocelli, or "delicate chemical sensing", to account for the mimic's ability to cope with such a large number of variables in its model's appearance,[4] including the ability to mimic the foliage of an artificial host plant made of plastic.[5] Another plant that could well be a cryptic mimic of its host is the parasitic Australian mistletoe, Amyema cambagei, which has an "uncanny resemblance" to the foliage of Casuarina trees.[6]
A rare 47 million year old fossil of a phasmid leaf insect from Germany demonstrates that leaf mimicry existed in this group in the Eocene period.[7] Among the orthoptera (grasshoppers and allies), fossil grigs (Prophalangopsidae) have been found in the Daohugou Biota of northeastern China, some 163.5 million years ago in the Jurassic period. Their forewings were patterned to resemble leaves of the cycad-like Bennettitales.[8] Jurassic lacewings (Neuroptera) of the genus Bellinympha from the Jiulongshan Formation in the same region similarly have their wings resembling pinnatecycad or Bennettitales leaves.[9]
Extant
Many extant insects masquerade as leaves.[8] Examples include moths and butterflies such as Kallima[10]many katydids,[11] the leaf mantises such as Choeradodis,[12] and the leaf insects (Phyllidae) among the phasmids.[13] Mimicry is not limited to coloration; behaviour, such as lying still or apparently fluttering in the wind, contributes to the camouflaging effect. Hugh Cott gives the example of Phyllium leaf insects which may hang from a leaf stalk by two or three legs, slowly turning "so as to suggest the motions of a leaf just ready to fall".[14]
The comma butterfly of Europe has summer and winter forms (seasonal polyphenism). Insects in the darker winter form tend to roost on tree trunks, whereas the lighter summer form insects always roost on leaves. The two morphs appear to camouflage the insects well in the two seasons.[15]
In 2016, arachnologists observed a species of orb web spider in southern China that mimics a leaf. The spider is brownish-green, teardrop-shaped, and has stripes which resemble leaf veins. It also decorates its web with dried leaves, which may help further disguise it. As of 2016[update] the species has not been fully described nor assigned a scientific name. It is the first identified instance of leaf mimicry in spiders.[16][17]
In vertebrates
Among the leaffishes (Polycentridae),[18] the Amazon leaffish (Monocirrhus polyacanthus) strongly resembles a dead leaf, and has the habit of lying on its side without moving, often at an angle, and remains motionless even if caught in a net. It swims with its body rigid, undulating its very narrow anal and dorsal fins, which according to Hugh Cott are "colourless and transparent, and so practically invisible".[19] The species is carnivorous, using its mimicry to approach its prey before engulfing it in its large jaws. Cott describes this form of mimicry as "special aggressive resemblance".[19]
↑ Castner, James; Nickle, David (August 2004). "Notes on the biology and ecology of the leaf-mimicking katydid Typophyllum bolivari Vignon (Orthoptera: Tettigoniidae: Pseudophyllinae: Pterochrozini)". Journal of Orthoptera Research. 4: 105–109.
This page is based on this Wikipedia article Text is available under the CC BY-SA 4.0 license; additional terms may apply. Images, videos and audio are available under their respective licenses.
